CFA632 USB Linux SendByte() failed


New member

I am trying the CFA632 test program, and I saw that sometimes the LCD does not print a character, and in my Linux console I get the "SendByte() failed" message.

I've modified the program, adding a little sleep time after each character sent.
Here is the code:
void SendString(char *data)
Now it sends the characters correctly, but the result is a slowdown in the speed in printing to the display.

How can I assure that the characters arrives well in the display without the slowdown?


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New member
Slackware Linux 11, kernel (shipped with the distro)

I have also noted that, even with the sleep, the display stop to respond (give me the "SendByte() failed" message) after some time of displaying strings (I am trying to simulate a clock, displaying a name in the first row and the clock in the second one, refreshing the clock every 1 minute).

CF Tech

I do not know much about Linux, but I would think it almost has to be in the USB system somewhere.

Can you try lcdProc or LCD4Linux and see if either of those work reliably?


New member
I think that I've found the solution...

I was using the "uchi" USB Host Controller Driver (Known as the "Alternative JE"), but my USB subsystem works better with the "usb-uhci" driver (known as "Intel Standard").

I've also reduced the usleep time to 10, and now I'm happy with the result :D (however, without the "usleep", sometimes my system cannot send at least 1 character to the display, resulting in an incomplete message. Then, I prefer a little delay with a complete message than displaying it instantaneously but incomplete).

Thanks you very much

CF Mark

The usleep() function is similar to the Windows Sleep() function in that itll normally sleep for a longer time period than what you specify.

Ie, the Windows Sleep() function is pretty useless at giving an accurate sleep period below 10ms.

I would be surprised if a normal Linux kernel would give anything better than 1ms accuracy normally (ie, usleep(1000)).